Mobile computing devices are becoming increasingly popular in modern society. As device manufacturers are now making millions of mobile computing devices, there is increasing demand for devices with improved performance and features. Battery performance is one area that may limit device performance. Batteries convert chemical energy into electrical energy to power a mobile device in various operational modes. A battery is typically designed to have a particular power, voltage, and current rating that relate to a capacity of the battery for supplying charge to a mobile device during use. By way of example, lithium-ion batteries are popular amongst device manufactures due to their high energy density and low rate of self-discharge. However, the terminal voltage of a lithium-ion battery type typically varies during discharge, due in part to its physical and chemical characteristics.
Large and/or sudden changes to the terminal voltage of a battery may result in an unexpected power down of a mobile device. For example, if the battery terminal voltage drops below the minimum operating voltage of a mobile device (or a subsystem thereof), the mobile device may lose power (or the subsystem may brown out). The change in battery terminal voltage may be dependent upon the impedance of the battery as well as the load current drawn from the battery. Specifically, the likelihood of a shutdown occurring for a given load increases as the impedance of the battery increases. The impedance of a battery is dependent upon a number of factors, such as the battery's size, chemical properties, age, temperature, discharge current, etc. Accordingly, what is needed is a power management solution that can monitor power system performance at a mobile device and reduce unexpected power down events.